1. Field of the Invention
The present invention relates to a semiconductor device including a non-volatile memory cell having a floating gate electrode and a control gate electrode, and its manufacturing method.
2. Background Art
As one of semiconductor storage devices, there is a non-volatile semiconductor memory. In recent years, demand for non-volatile semiconductor memories serving as data storing devices has become great. As representative electrically rewritable non-volatile memories using a floating gate electrode, NOR flash memories and NAND flash memories are known.
As for a memory cell in a conventional NAND flash memory, an active area, a tunnel insulation film, and a floating gate electrode are formed, for example, as heretofore described (see, for example, Japanese Patent Laid-Open No. 2006-186073).
First, a thermal oxidation film is formed on a silicon substrate, and a polycrystalline silicon layer is formed on the thermal oxidation film. Then, a resist pattern is formed on the polycrystalline silicon layer.
Thereafter, the polycrystalline silicon layer, the thermal oxidation film, and the silicon substrate are etched successively by the dry process, such as, for example, RIE (Reactive Ion Etching) using the resist pattern as a mask. As a result, the active area, the tunnel insulation film, and the floating gate electrode are formed in a self-aligned manner.
At the time of the dry process, both ends of the tunnel insulation film are subjected to plasma damages. As a result, characteristics of the non-volatile memory cell might be degraded.